This invention relates to a battery of coke ovens and to a method for repairing batteries of old coke ovens.
As shown in cross-section in FIG. 1, batteries of coke ovens generally consist of a central coal distillation area 1, a front or machinery area 2 and a rear coke discharge area 3. Central area 1 includes essentially a battery of ovens constructed on a foundation 4 and comprising a regenerator 5 and, at 7, a series of oven cells 8 spaced along in the longitudinal direction. The cells are bounded by piers 9 on each side and extend from the front to the rear of the battery. See FIG. 2.
The oven cells 8 contain the coal to be distilled and have upper inlets 10 for charging coal to the cells from the hoppers 11 of a charger 12, in the case of a gravity charger.
As shown in FIGS. 2 and 3, piers 9 are divided from the front of the battery and towards the rear by a succession of spacer elements 13 forming flues 14 which are supplied with air and a combustible gas. The heat liberated by the combustion of the gas distills the coal in the adjacent oven cells 8.
The front area 2 consists of a discharger 15, movable longitudinally with respect to the oven battery on rails 15.sub.1. The discharger is provided with a ram 15.sub.2 movable in the direction of the arrow F, that penetrates through the front opening 8.sub.2 of each oven cell 8 to push the coke cake out of this cell through the cell's rear opening 8.sub.1. Movement of the discharger 15 on rails 15.sub.1 thus permits ram 15.sub.2 to be positioned opposite the various oven cells in order to push the coke cake out the cell after the distillation of the coal.
The front area 2 also includes, as shown in FIG. 1, a collector 16 for the gas produced during the distillation of the coal, this gas being fed to the collector through a rising column 16.sub.1 and a cylinder 16.sub.2.
The rear area of the battery of coke ovens includes a coke guide 17 movable longitudinally on rails 17.sub.1 so that it can be positioned in front of the rear opening 8.sub.1 of the oven cell 8 to be discharged. A coke truck 18 is also movable longitudinally along the battery on rails 18.sub.1 so that, during the discharging of an oven cell 8 by the ram 15.sub.2, the coke cake is deposited in a layer of uniform thickness on the coke truck 18, which moves in synchronism with the fall of the coke.
The rear area 3 also includes a coke platform 19 onto which the coke in the truck 18 is poured to cool it.
The flues 14 between cell walls 9 are supplied with air and with gas in alternate cycles. The supply of air occurring through the intermediary of the cells of the regenerator so that the air supplying half the flues is heated by the cells of the regenerator which were heated during the previous cycle by the smoke resulting from the combustion of the gas.
The piers 9, alternating with the oven cells 8, are made as shown in FIG. 2, which is a horizontal section along A--A of FIG. 1, and in perspective in FIG. 3.
The piers 9 which separate the oven cells 8 are made of bricks surrounded by a vertical metallic frame 21. The rear openings 8.sub.1 of the cells 8 have doors 22 which can be opened to discharge the coke cake.
The construction of the piers consists of superposed bricks 23.sub.1, 23.sub.2, 23.sub.3, etc. which form the vertical walls 24 separating the flues 14 from the oven cells 8. Each wall consists of stretchers 25 and headers 26, the stretchers 25 being arranged along the height of the flues 14, whereas the headers 26 extend across the piers on the same course forming the spacers 13. Moreover, the two adjacent stretchers 25 in any one course having their joint plane 27 located in the center of the end faces of the headers 26 in the courses immediately above and below the stretchers.
These coke oven batteries frequently exhibit, after some years of operation, deterioration of the walls 24, both on the rear side (coke side) and on the front side (machine side), and this deterioration extends over a length corresponding to several flues 14.
This deterioration, which includes scaled bricks, exposed joints or cracks at the height of the joints or in the bricks, is due to the repeated thermal shocks, to the deformation of the uprights of the reinforcing frames 21, and to the different expansion of certain parts of the structure which are subject to different temperature conditions.
Attempts have been made to remedy this deterioration by repacking the open joints or by spraying a refractory product onto the walls. Also the ovens have been sprayed with pressurized air laden with fine ceramically bonding dusts, in an attempt to seal or fill up the small cracks.
Eventually, however, the frequency of the necessary repairs is such that, instead of remedying the deterioration, the latter is further aggravated by the repetition of the thermal shocks. Also the ignition of the gases escaping through the doors or through the cracks of the walls creates overheating and aggravates the deformation of the uprights of the frames 21, thus further widening the cracks.
Ultimately one is faced with self-perpetuating deterioration, and then it is necessary to reconstruct the heads of the piers for a length corresponding to several flues on both the coke side 3 and on the machine side 2. Often the repair needed on the coke side is greater than on the machine side because of the abrasion effect of the coke during its discharge and because of the heating of the metallic parts which it causes.
Conventionally, the heads of the piers are reconstructed as follows:
The temperature of the piers 9 to be repaired, and that of the adjacent piers, is lowered to about 1,000.degree. C. The heat is shut off from the flues 14 which are required to be demolished and reconstructed, and the oven cells 8 adjacent to the piers to be repaired are walled up beyond the point at which repair is to be effected relative to the ends of the oven. The flues to be repaired are then demolished while protecting the air and gas inlets from falling rubbish.
If the repairs include that of the roof, the vaults and roof corresponding to the piers to be repaired are likewise demolished. Otherwise, before demolishing the flues, the bracing or the suspension of the vaults is effected.
The ends of the flues are then reconstructed, as shown in FIGS. 2 and 3, or as shown in FIGS. 4 and 5.
According to the first method as shown in FIGS. 2 and 3, cold new stretchers are embedded, at the rate of one course in two, between hot old headers. For example, assuming that the repair is effected up to the line 29 in FIG. 3, cold new stretchers 25.sub.1 are embedded between hot old headers 26.sub.1.
However, the ends of the cold new stretchers undergo expansion stresses in the course of its temperature rise as a result of its contact with the hot old headers and the stretchers have a tendency to shift horizontally, and especially vertically. On the other hand the hot old part no longer expands and therefore does not shift. Fresh cracks often then appear in the walls.
To prevent these cracks, it is necessary for each brick to take up its own expansion by compressing its matrix so that its expansion will not react upon adjoining bricks. This does not usually happen, however, and the expansions are mutually cumulative so that the bricks nevertheless undergo stresses due to the aggregate of the individual expansions.
According to the second method as shown in FIGS. 4 and 5, the walls 24 first are cut from top to bottom in a vertical plane 30 that passes through the center of the headers 26.
The end of the pier in front of the plane 30 is then demolished. When it is reconstructed, the hot old part of the wall 24 behind plane 30 and the cold new part in front of it are connected by a smooth vertical joint (30) which then permits the new part of the wall to slide vertically relative to the old part during its expansion. The fluid-tightness of this joint plane is ensured by the application of a refractory product.
However, this second method exhibits considerable disadvantages. The cutting of the pier along plane 30 inevitably shakes the whole pier, which is a complex assembly of bricks joined among themselves by kinds of tenons and mortises. This shaking runs the risk of seriously damaging the stability of the remaining part of the pier, particularly since this part of the structure is no longer in perfect condition.
Furthermore, this second method leads to a weakening of the headers 26, because their width has been reduced by half as a resulting of cutting along plane 30. Also it is extremely difficult to obtain a vertical sliding joint which is fluid-tight. Consequently, it is not possible to completely prevent the escape of gas into the flue or of smoke into the cells which again causes rapid deterioration of the walls and the necessity for persistent, substantial and difficult maintenance.
British Pat. No. 2,050,586 discloses a repairing process for repairing the walls consisting of vertically sawing away the damaged part of the pier along a plane that passes through a lateral face of the headers. Thus adjacent stretchers would be cut along this joint plane, and the part of the stretcher remaining is assembled with a repairing brick provided with an internal overlapping spline.
It is also known by French Pat. No. 2,304,660 to form a vertical joint plane along a vertical alignment of one of the faces of the headers and then to use linking up bricks which form the separation of the two flues adjacent to the joint plane. The stretchers thus do not join each other at the joint plane.